Presence of Cyclopropane Fatty Acids (CPFA) in Human Plasma

Cyclopropane fatty acids (CPFA), as cis-9,10- methyleneoctadecanoic and cis- 11,12- methyleneoctadecanoic acids, are unusual alicyclic fatty acids which occur in plants, fungi, or microorganisms both Gram-negative and Gram-positive as well as protozoa and Myriapoda. Some papers suggest that cyclopropane fatty acids are involved in the bacterial pathogenesis of infections and in the resistance of some bacterial strains as Lactobacillus sp., Escherichia Coli, Salmonella enterica, Staphilococcus aureus and Pseudomonas to different environmental stresses such as temperature changes, high osmolarity, solvents, acid pH and others as the presence of antibiotics or heavy metals in the culture medium. However, little is documented about the presence of CPFA in mammals. Recently, they were detected in milk and several dairy products, in bovine meat, in fish and in mushrooms. Our previous results showed that the most important food sources of CPFA were dairy products (mainly Grana Padano cheese) and bovine meat reaching concentration of 1g/kg order, while food processing, manufacturing, seasoning steps, fermentation as well as cooking did not affect CPFA content in the analyzed food matrices. Furthermore, CPFA intake from these foodstuffs should be considered dietary relevant in view of a possible physiological effect.

Actually, CPFA (mainly cyclopropaneoctanoic acid 2-hexyl) have been recently identified in both human serum and adipose tissue, suggesting that these fatty acids are efficiently absorbed and may play a physiological role in the human body.

Moreover, fatty acids containing cyclopropane rings have been reported to exert biological effects on lipid metabolism, kidney function, inflammation, and enzymes activity as cyclooxygenase and stearoyl-CoA desaturase. Previous results suggested that the synthesis of CPFA in microorganisms and in plants is regulated by the expression of CPFA synthase, which catalyse the addition of the methylene group from S-adenosylmethionine to double bond of the unsaturated fatty acids precursor. However, this enzyme has still not been identified in animals and humans. To the best of our knowledge, no information is present in literature about the fate of CPFA within the human body, and a thorough investigation of how CPFA can be metabolised and accumulate in humans is needed.

The aim of this investigation is to determine CPFA presence in human plasma after a CPFA-rich diet (with controlled intake of Grana Padano cheese and whole milk containing CPFA). Plasma of the volunteers will be collected at eight different timepoints for lipid extraction, CPFA identification and quantification by GC-MS. A preliminary pilot in vivo acute study will be performed (involving only 1 subject) for investigating the post-prandial response curve of CPFA after a portion of Grana Padano cheese.